While taxiing large commercial aircraft in congested airports, pilots cannot see their own aircraft's wingtips and find it difficult to accurately judge clearance past obstructions such as buildings, other aircraft, jetways, poles etc. Collisions with such obstructions have occurred every year for many years, and are becoming increasingly frequent as airports become more congested. Needless to say, collisions involving aircraft can cause significant damage which can be expensive, not only in terms of the required repairs, but in terms of the extra time that the aircraft must be out of service while under repair.
Attempts have been made to introduce aircraft ground collision avoidance systems. One example is described in U.S. Pat. No. 6,118,401 which uses radar and/or camera sensors in the wingtips to detect the proximity of objects to the wingtips and to generate an alert based on proximity of the objects.
However the success of such systems has been limited. One reason is that in particularly congested spaces, too many alerts are generated. The pilot may have to steer the aircraft through a very narrow gap. If the collision avoidance system regularly generates alerts for objects that the pilot is aware of and which may be close, but are not actually a collision risk, the pilot may start to pay less attention to the alerts, or even ignore them altogether. In such cases, errors of judgement can once again result in avoidable collisions and expensive damage to the aircraft and/or other objects.
Also, ideally a collision detection system should be able to be retrofitted onto an aircraft, preferably onto a range of aircraft types and should not affect other aircraft equipment. However, this means that the system must be able to operate with information that is available as standard, for example in the ARINC 429 specification. This information includes ground speed and heading, but not nose wheel steering angle, which makes prediction of the aircraft path difficult. Fitting additional sensors to supplement the standard available information adds to the cost and complexity of the system, making it less attractive.
Therefore currently most pilots rely purely on their own eyesight to judge the position of obstacles and the aircraft's current path so as to judge whether or not a collision is likely. This is a difficult task and results in an unacceptable number of collisions. However in order to achieve sufficient uptake, a successful system must be attractive both in terms of applicability and installation and in terms of appeal to pilots.